Principles Related to Practical Chemistry Flashcards for NEET — 20 cards

First 8 of 20 Principles Related to Practical Chemistry flashcards

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1. Card 1 of 20

   What reagent is used to confirm the presence of an alcoholic hydroxyl group, and what is the positive observation?

   Hint: C.A.N. test for alcohols.

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   Answer

   Ceric Ammonium Nitrate test. A positive result is the appearance of a red or pink color, indicating the formation of a complex.

2. Card 2 of 20

   How do you distinguish a phenolic hydroxyl group from an alcoholic one using a simple chemical test?

   Hint: Iron(III) chloride loves phenols.

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   Answer

   Use the Neutral $\text{FeCl}_3$ test. Phenols give a characteristic violet, green, or blue coloration due to the formation of an iron-phenol complex. Alcohols do not react.

3. Card 3 of 20

   What is the standard chemical test to detect the presence of a carbonyl group (aldehydes and ketones)?

   Hint: Brady's reagent.

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   Answer

   The 2,4-DNP (Brady's Reagent) test. Carbonyl compounds react to form a yellow, orange, or red precipitate of 2,4-dinitrophenylhydrazone.

4. Card 4 of 20

   What is the most reliable test for a carboxyl group ($-\text{COOH}$) and what gas is evolved?

   Hint: Acids react with carbonates to release a specific gas.

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   Answer

   The Sodium Bicarbonate ($\text{NaHCO}_3$) test. It produces brisk effervescence due to the evolution of $\text{CO}_2$ gas, which turns lime water milky.

5. Card 5 of 20

   Write the chemical formula of Mohr's salt. Is it a double salt or a complex salt?

   Hint: Contains iron, ammonium, sulfate, and 6 waters of crystallization.

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   Answer

   Formula: $\text{FeSO}_4 \cdot (\text{NH}_4)_2\text{SO}_4 \cdot 6\text{H}_2\text{O}$ (Ferrous ammonium sulfate). It is a double salt because it completely dissociates into its constituent ions ($\text{Fe}^{2+}, \text{NH}_4^+, \text{SO}_4^{2-}$) in aqueous solution.

6. Card 6 of 20

   Write the chemical formula of Potash Alum and state its primary use in practical chemistry.

   Hint: Potassium, Aluminum, Sulfate, and 24 waters.

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   Answer

   Formula: $\text{K}_2\text{SO}_4 \cdot \text{Al}_2(\text{SO}_4)_3 \cdot 24\text{H}_2\text{O}$. It is widely used for the purification of water (coagulation of impurities) and as a mordant in dyeing.

7. Card 7 of 20

   In the preparation of p-Nitroacetanilide from aniline, why is aniline first converted to acetanilide before nitration?

   Hint: Protection of the amino group.

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   Answer

   The $-\text{NH}_2$ group in aniline is highly activating and easily oxidized by conc. $\text{HNO}_3$. Acetylation protects the amino group, preventing oxidation and reducing its activating effect, thereby avoiding the formation of a tarry mixture and polysubstituted products.

8. Card 8 of 20

   What are the chemical reagents and the pH medium required for the preparation of Aniline Yellow dye?

   Hint: Aniline couples in acidic conditions.

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   Answer

   Reagents: Benzenediazonium chloride and Aniline. Medium: Mildly acidic (pH 4-5). The reaction is a diazo coupling reaction yielding p-Aminoazobenzene.